Heat exchange system, method, non-transitory storage medium, and vehicle

ABSTRACT

A heat exchange system includes a first thermal circuit, a second thermal circuit, and a controller. A first thermal circuit includes a first device, a first pump, and a first flow path and a second flow path configured to cool the first device. A second thermal circuit includes a second device, a second pump, and a third flow path and a fourth flow path configured to cool the second device. A controller is configured to switch, when the controller switches a flow path of the first thermal circuit from the first flow path to the second flow path and switches a flow path of the second thermal circuit from the fourth flow path to the third flow path, the fourth flow path to the third flow path and the first flow path to the second flow path.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to Japanese Patent Application No.2020-035020 filed on Mar. 2, 2020, incorporated herein by reference inits entirety.

BACKGROUND 1. Technical Field

The present disclosure relates to a heat exchange system that executesheat exchange of a device mounted on a vehicle, a method, anon-transitory storage medium, and a vehicle.

2. Description of Related Art

Japanese Unexamined Patent Application Publication No. 2014-080123 (JP2014-080123 A) discloses a vehicle heat management system thatsuppresses, when switching a flow path for circulating coolant (heatmedium) to a heat medium distribution device (e.g. a battery, anelectric motor, a chiller, a water cooling condenser), a fluctuation ofthe coolant temperature before and after the switching of thecirculation flow path.

In the system disclosed in JP 2014-080123 A, when a circulation flowpath of the heat medium distribution device is switched from a firstflow path to a second flow path, a valve that switches a pump that pumpsthe coolant and the circulation flow path is appropriately controlled soas to suppress mixing of the coolant flowing through the first flow pathand the coolant flowing through the second flow path in the flow path.

SUMMARY

In the vehicle heat management system disclosed in JP 2014-080123 A, thecirculation flow path is switched after a state where the coolant in thefirst flow path and the coolant in the second flow path temporarilymerge into each other in the circulation flow path. Accordingly, in astate where the first flow path and the second flow path are incommunication with each other, which occurs during the switching of thecirculation flow path, circulation of the coolant in the flow path maybe stopped, or the coolant in the flow path may flow in a reversedirection, due to a change in a flow path length and a difference indirections in which the coolant flows. The changes in the coolant flowas described above may result in insufficient cooling of the heat mediumdistribution device.

The present disclosure provides a heat exchange system that can suppressthat circulation of the coolant in the flow path is stopped or thecoolant in the flow path flows in the reverse direction when switchingthe circulation flow path.

A first aspect of the present disclosure is a heat exchange systemincluding a first thermal circuit, a second thermal circuit, and acontroller. The first thermal circuit includes a first device, a firstpump, a first flow path configured to circulate a first coolant pumpedby the first pump and cool the first device, and a second flow pathconfigured to circulate the first coolant via a common flow path that isshared by a plurality of thermal circuits and cool the first device. Thesecond thermal circuit includes a second device, a second pump, a thirdflow path configured to circulate a second coolant pumped by the secondpump and cool the second device, and a fourth flow path configured tocirculate the second coolant via the common flow path and cool thesecond device. The controller is configured to switch, when thecontroller switches a flow path of the first thermal circuit from thefirst flow path to the second flow path and switches a flow path of thesecond thermal circuit from the fourth flow path to the third flow path,the fourth flow path to the third flow path and the first flow path tothe second flow path.

In the first aspect above, the second flow path may be set longer thanthe first flow path in the first thermal circuit, and the controller maybe configured to, before switching the flow path of the first thermalcircuit from the first flow path to the second flow path, issue acommand to increase an amount of the first coolant pumped by the firstpump to the first flow path.

In the first aspect above, the fourth flow path may be set longer thanthe third flow path in the second thermal circuit, and the controllermay be configured to, after switching the flow path of the secondthermal circuit from the fourth flow path to the third flow path, issuea command to decrease an amount of the second coolant pumped by thesecond pump to the third flow path.

A second aspect of the present disclosure is a flow path switchingcontrol method executed by a computer of a heat exchange system. Theheat exchange system includes a first thermal circuit having a firstdevice, a first pump, a first flow path configured to circulate a firstcoolant pumped by the first pump and cool the first device, and a secondflow path configured to circulate the first coolant via a common flowpath that is shared by a plurality of thermal circuits and cool thefirst device and a second thermal circuit including a second device, asecond pump, a third flow path configured to circulate a second coolantpumped by the second pump and cool the second device, and a fourth flowpath configured to circulate the second coolant via the common flow pathand cool the second device. The control method includes switching, whena flow path of the first thermal circuit is switched from the first flowpath to the second flow path and a flow path of the second thermalcircuit is switched from the fourth flow path to the third flow path,the fourth flow path to the third flow path and the first flow path tothe second flow path.

A third aspect of the present disclosure is a non-transitory storagemedium storing instructions that are executable by one or moreprocessors in a computer of a heat exchange system including a firstthermal circuit having a first device, a first pump, a first flow pathconfigured to circulate a first coolant pumped by the first pump andcool the first device, and a second flow path configured to circulatethe first coolant via a common flow path that is shared by a pluralityof thermal circuits and cool the first device and a second thermalcircuit including a second device, a second pump, a third flow pathconfigured to circulate a second coolant pumped by the second pump andcool the second device, and a fourth flow path configured to circulatethe second coolant via the common flow path and cool the second device,and that cause the one or more processors to perform functions. Thefunctions include switching, when a flow path of the first thermalcircuit is switched from the first flow path to the second flow path anda flow path of the second thermal circuit is switched from the fourthflow path to the third flow path, the fourth flow path to the third flowpath and the first flow path to the second flow path.

A fourth aspect of the present disclosure is a vehicle including a heatexchange system. The heat exchange system includes a first thermalcircuit, a second thermal circuit, and a controller. The first thermalcircuit includes a first device, a first pump, a first flow pathconfigured to circulate a first coolant pumped by the first pump andcool the first device, and a second flow path configured to circulatethe first coolant via a common flow path that is shared by a pluralityof thermal circuits and cool the first device. The second thermalcircuit includes a second device, a second pump, a third flow pathconfigured to circulate a second coolant pumped by the second pump andcool the second device, and a fourth flow path configured to circulatethe second coolant via the common flow path and cool the second device.The controller is configured to switch, when the controller switches aflow path of the first thermal circuit from the first flow path to thesecond flow path and switches a flow path of the second thermal circuitfrom the fourth flow path to the third flow path, the fourth flow pathto the third flow path and the first flow path to the second flow path.

In the fourth aspect, the second flow path may be set longer than thefirst flow path in the first thermal circuit, and the controller isconfigured to, before switching the flow path of the first thermalcircuit from the first flow path to the second flow path, issue acommand to increase an amount of the first coolant pumped by the firstpump to the first flow path.

In the fourth aspect, the fourth flow path may be set longer than thethird flow path in the second thermal circuit, and the controller may beconfigured to, after switching the flow path of the second thermalcircuit from the fourth flow path to the third flow path, issue acommand to decrease an amount of the second coolant pumped by the secondpump to the third flow path.

According to the first aspect, the second aspect, the third aspect, andthe fourth aspect of the present disclosure, the circulation flow pathis switched such that the coolant in the first flow path does nottemporarily merge into the coolant in the second flow path in the flowpath. Therefore, stop of the circulation of the coolant in the flow pathand reverse flow of the coolant in the flow path can be suppressed.

BRIEF DESCRIPTION OF THE DRAWINGS

Features, advantages, and technical and industrial significance ofexemplary embodiments of the disclosure will be described below withreference to the accompanying drawings, in which like signs denote likeelements, and wherein:

FIG. 1 is a functional block diagram showing a schematic configurationof a heat exchange system according to an embodiment;

FIG. 2 is a diagram illustrating a detailed configuration of a firstthermal circuit and a second thermal circuit

FIG. 3 is a diagram illustrating a flow path state of each thermalcircuit before switching the flow path;

FIG. 4 is a diagram illustrating a flow path state of each thermalcircuit after switching the flow path;

FIG. 5 is a flowchart showing a processing procedure of flow pathswitching control executed by a control unit of the heat exchangesystem;

FIG. 6A is a diagram illustrating a procedure for switching a flow pathstate of each thermal circuit;

FIG. 6B is a diagram illustrating a procedure for switching a flow pathstate of each thermal circuit;

FIG. 6C is a diagram illustrating a procedure for switching a flow pathstate of each thermal circuit;

FIG. 7 is an application example of a configuration of a thermalcircuit; and

FIG. 8 is an application example of a connection mode of thermalcircuits.

DETAILED DESCRIPTION OF EMBODIMENTS

A heat exchange system according to the present disclosure executes acooperative control, in a plurality of thermal circuits having a commonflow path as a part of a flow path for circulating coolant, by switchingthe flow path of each thermal circuit and adjusting an amount of thecoolant in the flow path so as to suppress stop of the circulation ofthe coolant in the flow path and a reverse flow of the coolant in theflow path.

Embodiment

Configuration

FIG. 1 is a functional block diagram showing a schematic configurationof a heat exchange system 1 according to an embodiment of the presentdisclosure. The heat exchange system 1 illustrated in FIG. 1 includes afirst thermal circuit 10, a second thermal circuit 20, and a controlunit 50. FIG. 2 is a diagram illustrating a detailed configuration ofthe first thermal circuit 10 and the second thermal circuit 20 shown inFIG. 1. The heat exchange system 1 can be mounted on a vehicle such asan automobile using an internal combustion engine as a power source or ahybrid vehicle (HV) using an electric motor as a power source.

The first thermal circuit 10 is a thermal circuit capable of heatexchange using a heat medium. The first thermal circuit 10 includes afirst flow path R1, a second flow path R2, a first device 11, a firstpump 12, and a first switching valve 13. The first device 11, the firstpump 12, and the first switching valve 13 are connected with each otherby the first flow path R1 and the second flow path R2 such that a firstcoolant (or refrigerant) that is a heat medium can be circulated.

The first device 11 is a device to be cooled using the first coolantcirculating in the first flow path R1 or the second flow path R2.Examples of the first device 11 mounted on the vehicle include abattery, an electric motor, a chiller, and a water-cooled condenser.

The first pump 12 is a device that adjusts an amount of the firstcoolant to be pumped to the first flow path R1 or the second flow pathR2 such that the coolant is circulated in the first flow path R1 or thesecond flow path R2. The control unit 50 issues a command on the amountof the first coolant to be pumped by the first pump 12 into the flowpath.

The first switching valve 13 is a three-way valve for selectivelyswitching which of the first flow path R1 and the second flow path R2the first coolant pumped by the first pump 12 is circulated in.Specifically, the first switching valve 13 includes an inlet port aconnected to the discharge side of the first pump 12, an outlet port bconnected to the suction side of the first pump 12, and an outlet port cconnected to a common flow path 30 that will be described later. Thefirst flow path R1 is established by switching to a state where theinlet port a and the outlet port b communicate with each other, and thesecond flow path R2 is established by switching to a state where theinlet port a and the outlet port c communicate with each other. Thecontrol unit 50 controls the switching of the first switching valve 13.Further, a three-way valve of the related art may be used as the firstswitching valve 13.

The first flow path R1 and the second flow path R2 are flow pathsthrough which the first coolant flows. The first switching valve 13switches between the first flow path R1 and the second flow path R2. Thefirst flow path R1 is a circulation flow path in which the first coolantpumped by the first pump 12 returns to the first pump 12 via the firstdevice 11 and the first switching valve 13. The second flow path R2 is acirculation flow path in which the first coolant pumped by the firstpump 12 returns to the first pump 12 via the first device 11, the firstswitching valve 13, and the common flow path 30. A part of the flow pathto which the first device 11 and the first pump 12 are connected isshared between the first flow path R1 and the second flow path R2.Further, the second flow path R2 is longer (has a larger flowresistance) than the first flow path R1 because the second flow path R2includes the common flow path 30.

The second thermal circuit 20 is a thermal circuit capable of heatexchange using a heat medium. The second thermal circuit 20 includes athird flow path R3, a fourth flow path R4, a second device 21, a secondpump 22, and a second switching valve 23. The second device 21, thesecond pump 22, and the second switching valve 23 are connected witheach other by the third flow path R3 and the fourth flow path R4 suchthat a second coolant (or refrigerant) that is a heat medium can becirculated. The second coolant may be the same substance as the firstcoolant.

The second device 21 is a device to be cooled using the second coolantcirculating in the third flow path R3 or the fourth flow path R4.Examples of the second device 21 mounted on the vehicle include abattery, an electric motor, a chiller, and a water-cooled condenser.

The second pump 22 is a device that adjusts an amount of the secondcoolant to be pumped to the third flow path R3 or the fourth flow pathR4 such that the coolant is circulated in the third flow path R3 or thefourth flow path R4. The control unit 50 issues a command on the amountof the second coolant to be pumped by the second pump 22 into the flowpath.

The second switching valve 23 is a three-way valve for selectivelyswitching which of the third flow path R3 and the fourth flow path R4the second coolant pumped by the second pump 22 is circulated in.Specifically, the second switching valve 23 includes an inlet port dconnected to the discharge side of the second pump 22, an outlet port econnected to the suction side of the second pump 22, and an outlet portf connected to the common flow path 30 that will be described later. Thethird flow path R3 is established by switching to a state where theinlet port d and the outlet port e communicate with each other, and thefourth flow path R4 is established by switching to a state where theinlet port d and the outlet port f communicate with each other. Thecontrol unit 50 controls the switching of the second switching valve 23.Further, a three-way valve of the related art may be used as the secondswitching valve 23.

The third flow path R3 and the fourth flow path R4 are flow pathsthrough which the second coolant flows. The third flow path R3 and thefourth flow path R4 are switched by the second switching valve 23. Thethird flow path R3 is a circulation flow path in which the secondcoolant pumped by the second pump 22 returns to the second pump 22 viathe second device 21 and the second switching valve 23. The fourth flowpath R4 is a circulation flow path in which the second coolant pumped bythe second pump 22 returns to the second pump 22 via the second device21, the second switching valve 23, and the common flow path 30. A partof the flow path to which the second device 21 and the second pump 22are connected is shared between the third flow path R3 and the fourthflow path R4. Further, the fourth flow path R4 is longer (has a largerflow resistance) than the third flow path R3 because the fourth flowpath R4 includes the common flow path 30.

The common flow path 30 is a portion shared by the second flow path R2of the first thermal circuit 10 and the fourth flow path R4 of thesecond thermal circuit 20. The common flow path 30 is provided at alocation that is a part of the second flow path R2 through which thefirst coolant does not flow when the first flow path R1 is selected, anda part of the fourth flow path R4 in which the second coolant does notflow when the third flow path R3 is selected. An example of the commonflow path 30 is a heat exchanger such as a radiator.

The control unit 50 controls each of switching of the first switchingvalve 13 of the first thermal circuit 10 and switching of the secondswitching valve 23 of the second thermal circuit 20. Further, thecontrol unit 50 issues a command of the amount of the first coolantpumped by the first pump 12 of the first thermal circuit 10 to the firstflow path R1 or the second flow path R2, and a command of the amount ofthe second coolant pumped by the second pump 22 of the second thermalcircuit 20 to the third flow path R3 or the fourth flow path R4. Thecommand for switching of the valve and the command for the pump executedby the control unit 50 will be described later.

The control unit 50 is typically configured as an electronic controlunit (ECU) including a processor such as a microcomputer, a memory, andan input-output interface, and functions can be realized as theprocessor reads and executes a program stored in the memory.

Control

Flow path switching control executed by the heat exchange system 1according to the embodiment will be described with reference to FIGS. 3to 6C. The flow path switching control according to the embodiment isadvantageous for switching a state where the flow path of one of thefirst thermal circuit 10 and the second thermal circuit 20 uses thecommon flow path 30 and the flow path of the other of the first thermalcircuit 10 and the second thermal circuit 20 does not use the commonflow path 30 to a state where the flow path of the one of the firstthermal circuit 10 and the second thermal circuit 20 does not use thecommon flow path 30 and the flow path of the other of the first thermalcircuit 10 and the second thermal circuit 20 uses the common flow path30.

In the following example, the case where the state of the flow paths ofthe first thermal circuit 10 and the second thermal circuit 20 beforeswitching the flow paths is the state of the first flow path R1 and thefourth flow path R4 shown in FIG. 3, and the state of the flow paths ofthe first thermal circuit 10 and the second thermal circuit 20 afterswitching the flow paths is the state of the second flow path R2 and thethird flow path R3 shown in FIG. 4 will be described.

FIG. 5 is a flowchart showing a processing procedure of the flow pathswitching control executed by the control unit 50 of the heat exchangesystem 1. FIGS. 6A to 6C are diagrams for describing a procedure toswitch the flow path state (the first flow path R1 and the fourth flowpath R4) shown in FIG. 3 to the flow path state (the second flow path R2and the third flow path R3) shown in FIG. 4.

In the state before the flow paths are switched (FIG. 3 and the leftdiagram of FIG. 6A), a command value of a unit flow rate (the upperright chart in FIG. 6A) that is a flow rate per unit time of the flowpath of the first coolant in the first flow path R1 with respect to thefirst pump 12 of the first thermal circuit 10 and a command value of aunit flow rate (the lower right chart in FIG. 6A) that is a flow rateper unit time of the flow path of the second coolant in the fourth flowpath R4 with respect to the second pump 22 of the second thermal circuit20 are stable at constant values. From the state above, the control unit50 switches the flow paths in the following procedure.

Step S501: The control unit 50 of the heat exchange system 1 controlsthe command value of the unit flow rate of the first coolant in thefirst thermal circuit 10, which is a thermal circuit that does not usethe common flow path 30. Specifically, the second flow path R2 after theswitching is longer than the first flow path R1 before the switching,and the flow resistance thus increases in the second flow path R2.Therefore, the control unit 50 issues a command to the first pump 12 ofthe first thermal circuit 10 to increase the amount of the first coolantpumped to the first flow path R1. With the command above, the commandvalue of the unit flow rate of the first coolant in the first flow pathR1 is controlled to increase (the upper right chart in FIG. 6B). Thecommand above is issued so as to avoid that the unit flow rate of thefirst coolant in the second flow path R2 after switching of the flowpath in the first thermal circuit 10 from the first flow path R1 to thesecond flow path R2 is reduced to fall below a predetermined referencevalue even when the flow path through which the first coolant circulatesbecomes longer and the flow resistance is accordingly increased. It isdesirable to make the unit flow rate of the first coolant constant as aresult of changing the command value of the unit flow rate of the firstcoolant for the first pump 12 in accordance with a fluctuation of theflow resistance that occurs in accordance with the length of the flowpath through which the first coolant circulates. Therefore, thereference value above is typically the unit flow rate of the firstcoolant in the first flow path R1 before the command is issued to thefirst pump 12 for increasing the amount of the first coolant pumped bythe first pump 12. However, the reference value may be the unit flowrate of the first coolant required to cool the first device 11.

The command for the first pump 12 to increase the amount of the firstcoolant to be pumped can be issued by making a correction withmultiplying the current command value for the first pump 12 by apredetermined coefficient (=1 or more) or by adding a predeterminedcorrection value to the current command value for the first pump 12. Thecoefficient and the correction amount can be derived based on adifference in length or a difference in flow resistance between thefirst flow path R1 and the second flow path R2, etc.

Step S502: The control unit 50 of the heat exchange system 1 switchesthe flow path of the second thermal circuit 20, which is a thermalcircuit using the common flow path 30. Specifically, the control unit 50controls the second switching valve 23 of the second thermal circuit 20to switch the flow path of the second thermal circuit 20 from the fourthflow path R4 to the third flow path R3 (the left diagram in FIG. 6B).With the switching (from the fourth flow path R4 to the third flow pathR3) above, the command value of the unit flow rate of the second coolantfor the second pump 22 is the same, but the flow path through which thesecond coolant of the second thermal circuit 20 circulates becomesshorter and the flow resistance is thus reduced. Therefore, the unitflow rate of the second coolant in the third flow path R3 temporarilyincreases. Further, with the switching above, the common flow path 30 isnot used by either the first thermal circuit 10 or the second thermalcircuit 20 and is in a separated state (the left diagram in FIG. 6B).

The processing in step S501 and the processing in step S502 describedabove are typically executed in parallel. However, the processing instep S501 may be executed first and then the processing in step S502 maybe executed, or the processing in step S502 may be executed first andthen the processing in step S501 may be executed.

Step S503: The control unit 50 of the heat exchange system 1 switchesthe flow path of the first thermal circuit 10. Specifically, the controlunit 50 controls the first switching valve 13 of the first thermalcircuit 10 to switch the flow path of the first thermal circuit 10 fromthe first flow path R1 to the second flow path R2 (the left diagram inFIG. 6C). With the switching (from the first flow path R1 to the secondflow path R2) above, the flow path through which the first coolant ofthe first thermal circuit 10 circulates becomes longer and the flowresistance thus increases. Therefore, the unit flow rate of the firstcoolant in the second flow path R2 fluctuates in a decreasing direction.Here, the command value of the unit flow rate of the first coolant forthe first pump 12 is increased in advance in step S501. Therefore, evenwhen the flow path through which the first coolant circulates becomeslonger and the flow resistance thus increases due to the switching ofthe flow path, the resultant unit flow rate of the first coolant in thesecond flow path R2 can be made constant. Therefore, the unit flow raterequired for cooling the first device 11 can be stably secured.

Step S504: The control unit 50 of the heat exchange system 1 controlsthe command value of the unit flow rate of the second coolant in thesecond thermal circuit 20. Specifically, the control unit 50 commandsthe second pump 22 of the second thermal circuit 20 to reduce the amountof the second coolant pumped to the third flow path R3. With the commandabove, the command value of the unit flow rate of the second coolant inthe third flow path R3 decreases (the lower right diagram of FIG. 6C).The command above is issued such that the unit flow rate of the secondcoolant in the third flow path R3 after switching of the flow path inthe second thermal circuit 20 from the fourth flow path R4 to the thirdflow path R3 becomes substantially equivalent to the unit flow rate ofthe second coolant in the fourth flow path R4 before the switching evenwhen the flow path through which the second coolant circulates becomesshorter and the flow resistance thus decreases.

The command for the second pump 22 to reduce the amount of the secondcoolant to be pumped by the second pump 22 can be issued by making acorrection with multiplying the current command value for the secondpump 22 by a predetermined coefficient (=less than 1) or by subtractinga predetermined correction value from the current command value for thesecond pump 22. The coefficient and the correction amount can be derivedbased on a difference in length and a difference in flow resistancebetween the third flow path R3 and the fourth flow path R4, etc.

The processing in step S503 and the processing in step S504 describedabove are typically executed in parallel. However, the processing instep S503 may be executed first and then the processing in step S504 maybe executed, or the processing in step S504 may be executed first andthen the processing in step S503 may be executed.

Further, the processing in step S501 and the processing in step S504above may be omitted when the unit flow rate of the coolant does notchange significantly before and after the switching of the flow path(there is no significant difference in the length of the circulationflow path).

When the unit flow rate of the first coolant in the second flow path R2after the switching of the flow path becomes substantially equivalent tothe unit flow rate of the first coolant in the first flow path R1 beforethe switching of the flow path, and the unit flow rate of the secondcoolant in the third flow path R3 after the switching of the flow pathbecomes substantially equivalent to the unit flow rate of the secondcoolant in the fourth flow path R4 before the switching of the flowpath, this routine of the flow path switching control is terminated.

The flow path switching control described above can be executed in theprocedure similar to the above even when a state where the flow path ofthe first thermal circuit 10 is the second flow path R2 and the flowpath of the second thermal circuit 20 is the third flow path R3 isswitched to a state where the flow path of the first thermal circuit 10is the first flow path R1 and the flow path of the second thermalcircuit 20 is the fourth flow path R4.

Application Example

The configuration of the thermal circuit to which the flow pathswitching control of the present disclosure can be applied is notlimited to the configuration of the first thermal circuit 10 and thesecond thermal circuit 20 shown in the drawings. When the thermalcircuit is a thermal circuit having a configuration in which a pluralityof flow paths is switchable and at least one of the flow paths serves asa circulation flow path including a common flow path that is shared by aplurality of the thermal circuits, and at least another one of the flowpaths serves as a circulation flow path not including the common flowpath, the flow path switching control of the present disclosure can beapplied. For example, thermal circuits having the configurations shownin FIG. 7 can be used.

Further, a connection mode of the thermal circuit to which the flow pathswitching control of the present disclosure can be applied is notlimited to the connection mode of the first thermal circuit 10 and thesecond thermal circuit 20 shown in the drawings. The flow path switchingcontrol of the present disclosure can be applied to any connection modein which one common flow path is shared by two or more thermal circuitsamong the plurality of thermal circuits. For example, connection modesof the thermal circuits as shown in FIG. 8 can be used.

Operations and Effects

As described above, the heat exchange system 1 according to theembodiment of the present disclosure includes the first thermal circuit10 and the second thermal circuit 20. The first thermal circuit 10includes the first flow path R1 that circulates the first coolant tocool the first device 11 and the second flow path R2 that circulates thefirst coolant via the common flow path 30 to cool the first device 11.The second thermal circuit 20 includes the third flow path R3 thatcirculates the second coolant to cool the second device 21 and thefourth flow path R4 that circulates the second coolant via the commonflow path 30 to cool the second device 21. In the heat exchange system1, when switching the flow path of the first thermal circuit 10 from thefirst flow path R1 to the second flow path R2 and switching the flowpath of the second thermal circuit 20 from the fourth flow path R4 tothe third flow path R3, the control to switch the fourth flow path R4 tothe third flow path R3 first and then switch the first flow path R1 tothe second flow path R2 is executed.

With the flow path switching control above, when switching from thestate where the coolant flows through the common flow path 30 in one ofthe thermal circuits to the state where the coolant flows through thecommon flow path 30 in the other of the thermal circuits, the flow pathof either of the thermal circuits is switched after the separated statewhere the coolant does not flow through the common flow path 30.Therefore, occurrence of unintended fluctuations in the flow rate thatcauses circulation of the coolant in the flow path to stop and thecoolant in the flow path to flow in a reverse direction can besuppressed because the coolant in the flow path in one of the thermalcircuit is suppressed from temporarily merging into the coolant in theflow path of the other of the thermal circuits in the common flow path30.

Further, in the heat exchange system 1 according to the embodiment, ineach thermal circuit, the command value of the unit flow rate of thecoolant pumped by the pump to the flow path is increased in advancebefore the flow path is switched when the flow path after the switchingis longer than the flow path before the switching. With the controlabove, when switching from a short flow path to a long flow path,falling of the unit flow rate of the coolant below the unit flow raterequired for cooling the device can be avoided. Therefore, deteriorationof performance to cool the device can be suppressed. Further, the unitflow rate of the coolant does not decrease during the switching of theflow path. Therefore, other controls, such as pump flow ratecompensation control, can be executed.

As described above, the heat exchange system 1 according to theembodiment executes the cooperative control by switching the flow pathsof the thermal circuits and adjusting the unit flow rate of the coolantin the flow path, thereby suppressing occurrence of parts damage andoutput limitation due to insufficient cooling of the device whileavoiding occurrence of unintended fluctuations in the flow rate in thethermal circuits.

Although one embodiment of the technique of the present disclosure hasbeen described above, the present disclosure can be interpreted as aflow path switching control method executed by a control unit includinga processor and a memory, a control program of the method, acomputer-readable, non-transitory storage medium that stores the controlprogram, or a vehicle on which the heat exchange system including thecontrol unit is mounted, for example, in addition to the heat exchangesystem.

The present disclosure can be used as a heat exchange system thatexecutes heat exchange of devices mounted on a vehicle.

What is claimed is:
 1. A heat exchange system, comprising: a firstthermal circuit including a first device, a first pump, a first flowpath configured to circulate a first coolant pumped by the first pumpand cool the first device, and a second flow path configured tocirculate the first coolant via a common flow path that is shared by aplurality of thermal circuits and cool the first device; a secondthermal circuit including a second device, a second pump, a third flowpath configured to circulate a second coolant pumped by the second pumpand cool the second device, and a fourth flow path configured tocirculate the second coolant via the common flow path and cool thesecond device; and a controller configured to switch, when thecontroller switches a flow path of the first thermal circuit from thefirst flow path to the second flow path and switches a flow path of thesecond thermal circuit from the fourth flow path to the third flow path,the fourth flow path to the third flow path and the first flow path tothe second flow path.
 2. The heat exchange system according to claim 1,wherein: the second flow path is set longer than the first flow path inthe first thermal circuit; and the controller is configured to, beforeswitching the flow path of the first thermal circuit from the first flowpath to the second flow path, issue a command to increase an amount ofthe first coolant pumped by the first pump to the first flow path. 3.The heat exchange system according to claim 1, wherein: the fourth flowpath is set longer than the third flow path in the second thermalcircuit; and the controller is configured to, after switching the flowpath of the second thermal circuit from the fourth flow path to thethird flow path, issue a command to decrease an amount of the secondcoolant pumped by the second pump to the third flow path.
 4. A flow pathswitching control method executed by a computer of a heat exchangesystem including a first thermal circuit having a first device, a firstpump, a first flow path configured to circulate a first coolant pumpedby the first pump and cool the first device, and a second flow pathconfigured to circulate the first coolant via a common flow path that isshared by a plurality of thermal circuits and cool the first device anda second thermal circuit including a second device, a second pump, athird flow path configured to circulate a second coolant pumped by thesecond pump and cool the second device, and a fourth flow pathconfigured to circulate the second coolant via the common flow path andcool the second device, the method comprising switching, when a flowpath of the first thermal circuit is switched from the first flow pathto the second flow path and a flow path of the second thermal circuit isswitched from the fourth flow path to the third flow path, the fourthflow path to the third flow path and the first flow path to the secondflow path.
 5. A non-transitory storage medium storing instructions thatare executable by one or more processors in a computer of a heatexchange system including a first thermal circuit having a first device,a first pump, a first flow path configured to circulate a first coolantpumped by the first pump and cool the first device, and a second flowpath configured to circulate the first coolant via a common flow paththat is shared by a plurality of thermal circuits and cool the firstdevice and a second thermal circuit including a second device, a secondpump, a third flow path configured to circulate a second coolant pumpedby the second pump and cool the second device, and a fourth flow pathconfigured to circulate the second coolant via the common flow path andcool the second device, and that cause the one or more processors toperform functions comprising switching, when a flow path of the firstthermal circuit is switched from the first flow path to the second flowpath and a flow path of the second thermal circuit is switched from thefourth flow path to the third flow path, the fourth flow path to thethird flow path and the first flow path to the second flow path.
 6. Avehicle comprising a heat exchange system including: a first thermalcircuit including a first device, a first pump, a first flow pathconfigured to circulate a first coolant pumped by the first pump andcool the first device, and a second flow path configured to circulatethe first coolant via a common flow path that is shared by a pluralityof thermal circuits and cool the first device; a second thermal circuitincluding a second device, a second pump, a third flow path configuredto circulate a second coolant pumped by the second pump and cool thesecond device, and a fourth flow path configured to circulate the secondcoolant via the common flow path and cool the second device; and acontroller configured to switch, when the controller switches a flowpath of the first thermal circuit from the first flow path to the secondflow path and switches a flow path of the second thermal circuit fromthe fourth flow path to the third flow path, the fourth flow path to thethird flow path and the first flow path to the second flow path.
 7. Thevehicle according to claim 6, wherein: the second flow path is setlonger than the first flow path in the first thermal circuit; and thecontroller is configured to, before switching the flow path of the firstthermal circuit from the first flow path to the second flow path, issuea command to increase an amount of the first coolant pumped by the firstpump to the first flow path.
 8. The vehicle according to claim 6,wherein: the fourth flow path is set longer than the third flow path inthe second thermal circuit; and the controller is configured to, afterswitching the flow path of the second thermal circuit from the fourthflow path to the third flow path, issue a command to decrease an amountof the second coolant pumped by the second pump to the third flow path.